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United States Patent |
6,170,400
|
Salort
|
January 9, 2001
|
Device for the cutting of nonmetallic parts by means of a pyrotechnic
expansion tube
Abstract
A pyrotechnic cutting device (14) is designed for directly cutting one or
two parts (10) made from a nonmetallic material, such as a composite
material. The device (14) comprises a pyrotechnic expansion tube, which
acts directly on the part or parts (10) to be cut, as well as an abutment
(40) placed on the other side of the part and facing the spacer (20)
installed alongside the tube. The abutment acts in the manner of an anvil
during the use or operation of the pyrotechnic expansion tube (16). Thus,
there is a clearly defined, well localized cutting of the part (10) along
the edge (42) of the abutment aligned with the face (21) of the spacer
(20) turned towards the tube (16).
Inventors:
|
Salort; Cedric (Ville d'Avaray, FR)
|
Assignee:
|
AEROSPATIALE SocieteNationale Industrielle (Paris, FR)
|
Appl. No.:
|
323829 |
Filed:
|
June 2, 1999 |
Foreign Application Priority Data
Current U.S. Class: |
102/378; 89/1.15; 102/312; 102/313 |
Intern'l Class: |
F42B 015/10; F42B 003/00 |
Field of Search: |
102/312,313,378
89/1.15
|
References Cited
U.S. Patent Documents
3453960 | Jul., 1969 | Qualls | 102/49.
|
3486410 | Dec., 1969 | Drexelius et al. | 89/1.
|
3698281 | Oct., 1972 | Brandt et al. | 89/1.
|
4314500 | Feb., 1982 | Hoppe | 89/1.
|
4685376 | Aug., 1987 | Noel et al. | 89/1.
|
4778009 | Oct., 1988 | Sumner et al. | 89/1.
|
4829901 | May., 1989 | Yates, Jr. | 89/1.
|
4885993 | Dec., 1989 | Hancock et al. | 102/312.
|
4901802 | Feb., 1990 | George et al. | 102/312.
|
5331894 | Jul., 1994 | Wassell et al. | 102/378.
|
5390606 | Feb., 1995 | Harris | 102/378.
|
5392684 | Feb., 1995 | Renfro et al. | 102/378.
|
Foreign Patent Documents |
0 246 958 | Nov., 1987 | EP.
| |
0 273 061 | Jul., 1988 | EP.
| |
2 598 769 | Aug., 1988 | FR.
| |
Primary Examiner: Nelson; Peter A.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed is:
1. Pyrotechnic cutting device comprising a pyrotechnic expansion tube
installed in a space formed between two parts and defined by at least one
spacer linking said two parts, so as to cut at least one of the parts
along at least one cutting line when the tube is used, wherein each part
to be cut is made from a nonmetallic material, an abutment being fixed
thereto, opposite to and facing the spacer, so that one edge of the
abutment extends along the cutting line.
2. Device according to claim 1, wherein the abutment is substantially
non-deformable.
3. Device according to claim 1, wherein the abutment is made from a
deformable material.
4. Device according to claim 3, wherein a maintaining member, made from a
deformable material, is fixed to each part to be cut, opposite to and
facing the pyrotechnic expansion tube, the maintaining member comprising
an edge extending along the cutting line and being prolonged on moving
away from said edge.
5. Device according to claim 4, wherein the abutment and maintaining member
are made from the same material as the part to be cut and said material is
a composite material formed from sheets of long fibres embedded in a resin
matrix.
6. Device according to claim 1, wherein said parts and the spacer are made
from the same nonmetallic material in monolithic form.
7. Device according to claim 1, wherein the spacer is fixed between the
parts by fixing means traversing the same.
8. Device according to claim 1, wherein only one of the two parts is to be
cut, the other part being a substantially non-deformable support part.
9. Device according to claim 1, wherein both parts are to be cut, said
space being defined by two spacers and an abutment being placed on each of
said parts facing a first of the spacers.
10. Device according to claim 9, wherein the two parts form skins of a
first sandwich structure and the two abutments form skins of a second
sandwich structure penetrated by the terminal portions of said parts.
11. Device according to claim 9, wherein the second spacer is fixed between
the parts at a location remote from the pyrotechnic expansion tube.
Description
TECHNICAL FIELD
The invention relates to a cutting device using a pyrotechnic expansion
tube for cutting at least one part, along a given cutting line.
Such a device can more particularly be used in the aeronautical and space
industries for controlling in a very short time the separation of two
structural elements, whilst ensuring the transmission of at times high
forces and stresses between said two elements, before the cutting takes
place.
PRIOR ART
When two metallic structures, between which forces, stresses or loads pass,
have to be irreversibly separated in a very short time and in remotely
controlled manner, use is currently made of pyrotechnic cutting devices
integrated into the junction zone between the two structures.
When a clean cutting is desired, i.e. with a minimum release of dust, use
is generally made of a cutting device including a pyrotechnic expansion
tube.
The expression "pyrotechnic expansion tube" designates a tight, deformable,
metallic tube in which runs a detonating cord or fuse. A flexible material
such as silicone rubber is interposed between the detonating fuse and the
envelope. Prior to firing, the envelope has an oblong cross-section, e.g.
in the form of an ellipse or flattened circle.
When the detonating fuse is fired, the shock wave propagating at very high
velocity along the tube deforms the envelope and tends to give it a
substantially circular cross-section.
Conventionally a pyrotechnic cutting device including a pyrotechnic
expansion tube is used for cutting metallic parts. It is therefore
installed in a space formed between two metallic parts or between two
portions of the same metallic part. The part or parts to be cut are
previously machined, so as to have a reduced thickness zone along each
desired cutting line. The expansion of the envelope caused by the firing
of the detonating fuse leads to the cutting of the part or parts along the
cutting line corresponding to the machined zone.
Devices for cutting one or two metallic parts by means of a pyrotechnic
expansion tube are described in the following documents: U.S. Pat. Nos.
3,486,410, 3,453,960, 3,698,281, FR-A-2 598 796 and EP-A-0 273 061.
The structural elements used in the aeronautical and space industries are
increasingly frequently made from nonmetallic materials. In particular,
the materials used are often composite materials, i.e. materials formed
from long fibres arranged in the form of superimposed sheets in preferred
orientations and embedded in a resin matrix.
When such nonmetallic materials are used, it is not at present possible to
directly cut them by means of a pyrotechnic expansion tube, as is normally
the case with metallic structures.
Firstly, the machining of a reduced thickness zone in a nonmetallic
material and in particular a composite material is at present
indispensable for localizing and limiting the cutting produced by the
pyrotechnic expansion tube, is unacceptable in a nonmetallic material,
particularly of the composite type Thus, such a machining would
unacceptably reduce the mechanical characteristics of the part prior to
its cutting, by cutting the long fibres leading to its characteristics.
Moreover, the cutting of a nonmetallic and in particular composite material
using a cutting device would possibly give rise to significant pollution
of the environment, as well as to a marked reduction in the mechanical
characteristics of the adjoining structures. This reduction would be due
to so-called delamination phenomena, i.e. a detachment or separation of
the fibre sheets in the vicinity of the cutting line.
For various reasons, when a pyrotechnic cutting device has at present to be
integrated into a nonmetallic structure, between the two structural
elements to be separated is interposed a metallic structure, whose cutting
with the aid of a pyrotechnic expansion tube is controlled. In other
words, separation is ensured by cutting one or more metallic parts joined
to the nonmetallic material structural assemblies which it is wished to
separate. This conventional arrangement makes the structure more
complicated and increases costs.
It is also contrary to one of the essential advantages brought about by
nonmetallic materials, namely the weight gain. Thus, the addition of
metallic parts to the linking zone between the two structural assemblies
to be separated leads to a non-negligible weight increase. This weight
increase is particularly due to the metallic nature of the added parts and
the indispensable presence of fixing members ensuring the connection
between the metallic parts and the nonmetallic parts. This is a
particularly prejudicial disadvantage in certain applications, such as the
space industry.
The pyrotechnic cutting of metallic parts also produces relatively severe
shocks. Such a shock is applied to often very sensitive instruments and
equipment located in the vicinity thereof. However, the very different
mechanical characteristics of nonmetallic materials would permit, if their
direct cutting was possible, the separation by producing a much lower
shock level. This would be an advantage for the embarked instruments and
equipment.
DESCRIPTION OF THE INVENTION
The invention relates to a pyrotechnic cutting device making it possible to
directly cut nonmetallic parts and in particular composite material parts
by means of a pyrotechnic expansion tube, whilst maintaining the
mechanical properties of such parts before and after their cutting and
whilst limiting the pollution produced during cutting.
According to the invention, this result is obtained by means of a
pyrotechnic cutting device comprising a pyrotechnic expansion tube
installed in a space formed between two parts and defined by at least one
spacer linking said two parts, so as to cut at least one of the parts
along at least one cutting line when the tube is used, characterized in
that each part to be cut is of a nonmetallic material, an abutment being
fixed thereto, opposite to and facing the spacer, so that one edge of the
abutment extends along the cutting line.
The abutment fixed to the outside of the part to be cut, facing the spacer,
acts in the manner of an anvil against which bears the corresponding
portion of the part during the firing of the detonating fuse. This ensures
a relatively clean and well localized cutting, without machining the
parts. Therefore the mechanical strength of the parts prior to cutting is
not cast into doubt. Moreover, the cleanness of the cut preserves the
integrity of the parts after cutting and greatly limits pollution.
By rendering possible the direct cutting of nonmetallic materials and in
particular composite materials, the device according to the invention
makes it possible to very significantly reduce the weight of the
nonmetallic assemblies to be cut with the aid of a pyrotechnic expansion
tube. Moreover, the device according to the invention makes it possible to
significantly reduce the shock level producing during cutting compared
with that produced during the cutting of metallic parts.
In a first embodiment of the invention, each abutment is substantially
non-deformable.
Conversely, in a second embodiment of the invention, each abutment is made
from a deformable material.
In order to even better preserve the integrity of the cut part and in
particular oppose its delamination in the case of a composite material
part, a maintaining member made from a deformable material is preferably
fixed to each part to be cut, opposite to and facing the pyrotechnic
expansion tube. The maintaining member then comprises an edge extending
along the cutting line and prolonged on moving away from said edge.
When the device comprises both an abutment and a maintaining member, said
two members can be made from the same material as the part to be cut and
said material is advantageously a composite material formed from sheets of
long fibres embedded in a resin matrix. The assembly is then produced
directly by covering during the manufacture of the part.
Moreover, the parts and the spacer can be made from the same nonmetallic
material in monolithic form. In other words, the pyrotechnic expansion
tube is then integrated into the assembly during the manufacture of the
parts.
Conversely, the spacer can be fixed between the parts by fixing means such
as bolts traversing the same.
All the variants and shapes according to the invention are applicable both
when one of the two parts is to be cut and when both parts are to be cut.
In the first case, the other part is a substantially non-deformable support
part, connected to the part to be cut by one or two spacers.
In the second case, the space in which is housed the pyrotechnic expansion
tube is defined by two spacers and an abutment is placed on each of the
parts to be cut, facing a first of the spacers.
In a particularly advantageous embodiment of the invention, the two parts
then form the skins of a first sandwich structure including a core, and
the two abutments form the skins of a second sandwich structure also
including a core. Terminal portions of the parts forming the skins of the
first sandwich structure then penetrate the second sandwich structure,
between the abutments and the second spacer.
In this case, the second spacer is fixed between the parts at a single
location, which is preferably remote from the pyrotechnic expansion tube.
BRIEF DESCRIPTION OF THE DRAWINGS
A description will now be given in non-limitative manner of embodiments
with reference to the attached drawings, wherein show:
FIG. 1 A sectional view diagrammatically showing a first embodiment of the
pyrotechnic cutting device according to the invention, according to which
the abutment is substantially non-deformable, in the case where a single
nonmetallic part is to be cut.
FIG. 2 A diagrammatic sectional view showing a variant of the cutting
device of FIG. 1, applied to the simultaneous cutting of two nonmetallic
parts.
FIG. 3 A diagrammatic sectional view comparable to FIG. 1, illustrating a
second embodiment of the invention, according to which the abutment is
deformable, in the case where the device also has a maintaining member.
FIG. 4 A diagrammatic sectional view showing a variant of the cutting
device of FIG. 3, applied to the simultaneous cutting of two nonmetallic
parts.
FIG. 5 A diagrammatic sectional view illustrating another embodiment of the
invention, in which two parts to be cut and two abutments respectively
form the skins of two sandwich structures which it is wished to separate.
DETAILED DESCRIPTION OF SEVERAL PREFERRED EMBODIMENTS OF THE INVENTION
In FIG. 1, reference numeral 10 designates a nonmetallic material part
which it is wished to cut along a cutting line 12. The nonmetallic
material from which is formed the part 10 can be of different natures
without passing outside the scope of the invention. A preferred
application relates to the case where said material is a composite
material, formed from sheets of long fibres embedded in a resin matrix. As
is well known to the expert, such parts can be obtained by covering sheets
of fibres impregnated with thermosetting resin, followed by the
polymerization of the resin.
The part 10 to be cut can have various shapes without passing beyond the
scope of the invention. In the case illustrated in FIG. 1, the part 10 is
in the form of a plate with a substantially uniform thickness. Said plate
can be planar, inwardly curved, or have any other shape adapted to the
envisaged application.
The observations made hereinbefore in connection with part 10 also apply to
the cutting line 12. In other words, the cutting of the part 10 can take
place along a straight, curved or other line without passing beyond the
scope of the invention.
In FIG. 1, the cutting device according to the invention is generally
designated by reference numeral 14. In this case, the cutting device
comprises a pyrotechnic expansion tube 16, a support part 18 and a spacer
20 (said two latter parts possibly being separate or in one piece, in the
manner shown).
The pyrotechnic expansion tube 16 is implemented in the same way as in
devices used for cutting metallic parts. However, it has reduced
dimensions adapted to the nature of the material constituting the part 10
to be cut, so as to produce a much lower shock wave than in the cutting
devices for metallic parts. Thus, there is no need for a detailed
description of the pyrotechnic expansion tube 16.
To facilitate understanding, it is merely pointed out that the pyrotechnic
expansion tube 16 comprises a tight, deformable, metallic envelope 22, a
detonating cord or fuse 24 housed in the envelope 22, as well as a
flexible material 26 interposed between the detonating fuse 24 and the
envelope 22. The function of the flexible material 26 is to center the
detonating fuse within the envelope. In exemplified manner, it can be made
from silicone rubber. Prior to firing the envelope 22 has an oblong
section, e.g. in the form of a flattened circle or oval, as illustrated in
FIG. 1.
The pyrotechnic expansion tube 16 is received in a space 28 formed between
the part 10 to be cut and the support part 18, said space 28 being defined
on one side by a face 21 of the spacer 20. More specifically, the longest
section of the envelope 22 is oriented parallel to the direction defined
by the part 10 to be cut.
In the embodiment illustrated in FIG. 1, the support part 18 and spacer 20
form a single part, separate from the part 10 to be cut. This single part
is fixed to the part to be cut by fixing means such as not shown bolts,
whose location is diagrammatically illustrated by the mixed line 30.
The nature and thickness of the materials constituting the support part 18
and spacer 20 are such that these two parts are substantially
non-deformable during the operation of the pyrotechnic expansion tube 16.
This result is obtained either by using non-deformable materials of
limited thickness, such as metals, or by using relatively flexible, but
more thick materials, such as nonmetallic materials, as is illustrated in
FIG. 1. In the latter case, as a variant the support part 18 and spacer 20
can be produced in one piece with the part 10 to be cut. There is then no
longer any need for the fixing means such as bolts 30.
In all cases, the face of the support part 18 turned towards the part 10 to
be cut constitutes a substantially non-deformable surface, which is
generally parallel to the part 10 and on which bears the pyrotechnic
expansion tube 16 during the firing of the detonating fuse 24.
Consequently the expansion of the envelope 22 entirely takes place in the
direction of the part 10 to be cut. In addition, the face 21 of spacer 20
turned towards the space 28 is aligned with the cutting line 12 of part
10.
It should be noted that the thickness of the pyrotechnic expansion tube 16
is substantially equal, apart from the installation clearance, to the
width of the space 28, between the part 10 to be cut and the support part
18. A not shown element can be joined to the support part 18, or formed
directly on said part in order to close the space 28 facing the spacer 20,
if this should be necessary for preventing the release of tube 16.
According to the invention, an abutment 40 is fixed to the part 10 to be
cut, facing the spacer 20 and opposite to the latter. The abutment 40 is
in the form of a plate, whereof one edge 42 extends along the cutting line
12 of part 10.
In the embodiment illustrated in FIG. 1, the abutment 40 is substantially
non-deformable. The non-deformable character of the abutment can be
obtained either by using a relatively thick, nonmetallic material, as
shown, or by using a reduced thickness, metallic material.
The not shown fixing means, whose location is indicated by the mixed line
30, effectively maintain the abutment 40 against part 10, in the vicinity
of the cutting line 12.
The presence of the abutment 40 ensures a precise, localized cutting, by
acting in the manner of an anvil on which bears the part 10 to be cut.
When the detonating fuse 24 is fired, the resulting shock wave brings about
the expansion of the envelope 22, which tends to assume a substantially
circular cross-section. In view of the fact that the pyrotechnic expansion
tube 16 bears on a substantially non-deformable part 18, its expansion
essentially takes place in the direction of the part 10 to be cut. It is
therefore totally applied to the part 10. In view of the fact that the
latter bears on the abutment 40 in its portion facing spacer 20, the
expansion of the tube 16 consequently precisely cuts the part 10 along the
previously defined cutting line 12.
Thus, there is a precise, perfectly localized cut of the part 10 made from
the nonmetallic material. In addition, said cut is relatively clean.
It should be noted that cutting essentially takes place by shearing, which
limits pollution. Moreover, such cutting by shearing requires a relatively
low pyrotechnic energy level in the case of a nonmetallic material and in
particular a composite material.
FIG. 2 shows a variant of the first embodiment of the invention described
hereinbefore relative to FIG. 1. This variant relates to the case where
the pyrotechnic cutting device 14 is used for simultaneously cutting two
parts 10, which are substantially parallel to one another and which define
between them a space 28. In this case, the space 28 is closed opposite to
the spacer 20, e.g. by a second spacer 36. The spacer 36 is fixed to the
parts 10 by fixing means such as not shown bolts, whose location is
diagrammatically illustrated by the mixed line 38 in FIG. 2.
As a variant, the spacer 36 can be in one piece with the two parts 10 or
replaced by the direct junction of said two parts, which are then joined
together.
In the constructional variant of FIG. 2, an abutment 40 is fixed to the
outer face of each of the two parts 10, facing the spacer 20. More
specifically, an edge 42 of each of the abutments 40 is aligned with the
cutting line 12 provided in each of the parts 10 and consequently with the
face 21 of spacer 20 turned towards the space 28.
It should be noted that the localization of the cutting along the cutting
lines 12 is made easier if the portions of the parts 10 in contact with
the pyrotechnic expansion tube 16 are able to easily bend towards the
outside whilst pivoting about their anchoring point, diagrammatically
illustrated by the mixed lines 38 in FIG. 2. To this end, the fixing of
the parts 10 to the spacer 36 must take place as far away as possible from
the tube 16 and the cutting lines 12 provided in the parts. Conversely, as
in the embodiment of FIG. 1, it is desirable for the fixing of the
abutments 40 and parts 10 to the spacer 20, illustrated by the mixed lines
30, to be as close as possible to the cutting lines 12.
In the case of the variant of FIG. 2, the abutments 40 are substantially
non-deformable, as in the embodiment previously described relative to FIG.
1.
FIG. 3 diagrammatically shows a second embodiment of a pyrotechnic cutting
device 14 according to the invention. As in the case of FIG. 1, FIG. 3
illustrates the simplest case where the cutting only applies to a single
part 10. The general arrangement is consequently comparable to that
described hereinbefore relative to FIG. 1, so that there is no need for a
detailed description of the various parts in this case constituting the
cutting device 14.
A first difference is due to the fact that instead of being substantially
non-deformable, the abutment 40 is deformable and is made from a material
preferably identical or very close to the nonmetallic material from which
the part 10 to be cut is made.
Thus, when the part 10 is made from a composite material constituted by
sheets of long fibres embedded in a resin matrix, the abutment 40 can be
obtained by covering supplementary layers of thermosetting
resin-impregnated fibres. The abutment is then linked to the part 10 over
the entire surface adjacent thereto during the manufacture of the part.
In this case the orientation of the fibres in the abutment 40 can
significantly differ from that of the fibres in part 10, in order to take
account of the specific function of abutment 40. Thus, the fibres in the
abutment 40 are advantageously interlaced in order to ensure the taking up
again of the radial forces and stresses applied thereto during the
operation of the pyrotechnic expansion tube 10. Conversely, the fibres
placed in part 10 are generally largely oriented in the longitudinal
direction, so as to ensure the transmission of the stresses and forces
applied thereto mainly in said direction.
FIG. 3 shows an improvement to the cutting device according to the
invention. It should be noted that this improvement can also be used in
the previously described embodiment and variant.
According to this improvement, a maintenance or maintaining member 40 is
also fixed to the part 10, opposite to the pyrotechnic expansion tube 16
and facing the latter. The maintaining member 40 comprises an edge 46
extending along the cutting line 12. Said edge 46 is substantially in
contact with the edge 42 of abutment 40.
The maintaining member 44 is made from a deformable material in order to
follow the deformation of part 10 during its cutting controlled by the use
of the pyrotechnic expansion tube 16 and it extends over a certain
distance opposite to its edge 46.
The maintaining member 44 is advantageously made from a material identical
to that from which is formed the part 10 to be cut. In the At case where
the latter is a composite material, the maintaining member 44 can
consequently be directed integrated into the part during its manufacture,
in the same way as the abutment 40 in the embodiment of FIG. 3.
The functions of the maintaining member 44 are to maintain the integrity of
the corresponding portion of part 10 and absorb the shock during cutting.
It consequently further improves the cleanness of the cut. More
particularly in the case of a composite material, the maintaining member
maintains the integrity of the adjacent portion of part 10 following
cutting and opposes the delamination thereof.
FIG. 4 shows a pyrotechnic cutting device comparable to that described
hereinbefore relative to FIG. 3 and applied to the simultaneous cutting of
two parts 10.
In this case, the maintaining members 44 associated with the parts 10 to be
cut are fixed to a spacer 36 by fixing means such as the not shown bolts,
whose location is illustrated by the mixed lines 38 and whilst respecting
the same conditions as those described relative to FIG. 2. More
specifically, the fixing of parts 10 and maintaining members 44 to the
spacer 36 takes place at a location 38 relatively remote from the tube 16
and cutting lines 12 adjacent to the spacer 20 and the abutments 40. This
facilitates the bending of the parts 10 by pivoting about the
aforementioned fixing means, which is necessary for a good cutting by
shearing of the two parts along the spacer 20 and abutments 40.
When the cutting device 14 according to the invention ensures the
simultaneous cutting of two parts 10, as is the case in the variants of
FIGS. 2 and 4, the parts 10 can assume very varied shapes, outside the
junction zone containing the cutting device.
Thus, as shown in FIGS. 2 and 4, the two parts 10 can remain parallel to
one another and can be linked by a cellular structure 48, e.g. a honeycomb
structure. The parts 10 then constitute the skins of a sandwich structure,
whose core is formed by the cellular structure 48.
As a variant, the parts 10 can also be interconnected so as to form a
one-piece structure, outside the junction zone materialized by the device
14. In this case, the spacers 20 and 36 can optionally form integral
portions of said parts 10.
FIG. 5 shows another, particularly advantageous embodiment of the
invention. This embodiment differs from the previous embodiments by the
fact that the cutting device 14 according to the invention ensures the
joining of two sandwich structures 50, 52 prior to the utilization
thereof.
Thus, in the embodiment of FIG. 5, the two parts 10 to be cut form the
skins of a first sandwich structure 50, whose core is constituted by a
cellular material 48, e.g. a honeycomb material. The pyrotechnic expansion
tube 16 is housed in a space 28, which is free from cellular material and
located in the vicinity of one of the edges of the sandwich structure 50.
A spacer 36 defines the space 28 on the side of the cellular material 48.
Said spacer 36 is fixed between the parts 10 by fixing means such as the
not shown bolts, whose location 38 is as far away as possible from the
pyrotechnic expansion tube 16. Beyond the space 28 and tube 16, terminal
portions of the two parts 10 penetrate the second sandwich structure 52.
More specifically, the second sandwich structure 52 comprises two skins 40,
a cellular material, e.g. honeycomb material core 56 and a spacer 20
replacing the core 56 along the edge of said structure adjoining the first
sandwich structure 50.
The terminal portions of the two parts 10 penetrate between the skins 40
and spacer 20 and fixing means such as not shown bolts link the stack
formed in this way by the skins 40, parts 10 and spacer 20. These fixing
means are located at a location 30 as close as possible to the edges 42 of
skins 40 and face 21 of the spacer 20 turned towards the space 28.
Moreover, the edges 42 and face 21 are aligned along the cutting lines 12
provided in the parts 10.
In the embodiment of FIG. 5, the skins 40 of the second sandwich structure
52 fulfill the same function as the abutments in the previously described
embodiments. This is why they are designated by the same reference
numerals.
It should be noted that in the embodiment described relative to FIG. 5, it
is possible to integrate the pyrotechnic expansion tube 16 into the
structure, during the manufacture of the latter.
In general terms, the pyrotechnic cutting device 14 in all cases permits a
direct cutting of one or two nonmetallic material parts and in particular
composite material parts, along one or more clearly defined and well
localized cutting lines, under generally satisfactory cleanness
conditions.
It should be noted that the simultaneous cutting of two parts is preferable
whenever possible, as a result of the perfect symmetry then obtained in
the device. Thus, the energy required for ensuring cutting is then at a
minimum level.
In all cases, the cutting of nonmetallic material parts is ensured, whilst
maintaining the mechanical strength thereof prior to cutting due to the
absence of machining. In addition, the direct cutting of nonmetallic
materials leads to a significant reduction in the energy required for
cutting compared with the prior art procedure in which it was necessary to
cut intermediate metal parts. Consequently, the shock produced by cutting
is very significantly reduced, which is an important advantage relative to
installations and equipment which may to be embarked in the vicinity of
the device.
Finally, when the device comprises two pairs of parts (FIGS. 2 and 4), the
cutting lines 12 can be aligned with the same spacer 20, as has been
shown, or can be aligned with each of the spacers 20 and 36.
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